Classic/Antique Car Repair/6 volt vs 12 volt

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Expert: - 7/30/2008


Question
I own a 1938 Pontiac Sport Coupe 6 cylinder. What are the dangers of using a 12 volt battery to start the automobile vs a 6 volt battery.  I planed on using a relay to start the automobile with 12 volts and switch back to 6 volt to operate the automobile. It takes a lot of cranking to start the autobobile with the 6 volt battery. I am running an electric fuel pump for the first 10 seconds prior to starting the automobile.
Thanks,
William

Answer
There was a company around a dozen or so years ago that manufactured a battery system like you describe. I had one in a 41 Caddie that I bought and it worked fairly well. However when it came time to sell the car that system turned off a few buyers. So, I hauled the starter out, did a careful rebuild including new bushings that I hand fitted, and the car started fine, and sold for the price that I wanted. What you describe will work. The new fuel injected cars with computer control run the fuel pump from one to two seconds on key on and don't turn the pump back on till the engine is running.
Brad  

Classic/Antique Car Repair

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Brad Sears

Expertise

All automotive including antique and collectible. However if the car has been modified I can only answer in general terms and maybe get you pointed in the right direction.

Experience

Automotive tech instructor. Syndicated auto columnist 1970's though the early 1990's. Syndicated auto radio talk show, Ask Brad About cars, CBS Radio 70's through 90's TV Show "Last Chance Garage" 1980's PBS-TV syndicated. Auto instructor for the following companies: Fram Autolyte Holly Carter AMF Ford Motor University Of Conn Blue Hills Technical School Sugar River Technical Center Grew up in a family garage in Needham Mass and turned wrenches from the age of 14.

Publications
Manchester Union Leader, Nashua Telegraph, Motor Service Magazine, Yankee Magazine, Popular Mechanics (Saturday Mechanic early 80's), Los Angeles Times, New York Times, and lots more.

Education/Credentials
More than I care to remember. Basically Franklin Technical Institute in Boston, Northeastern University, Fitchburg State Teachers College, Tufts University, and a lot of factory schools along the way.

Awards and Honors
Moto Award winner. And much more.

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